HFC-236fa is useful as a refrigerant, fire extinguishant, heat transfer medium, gaseous dielectric, sterilant carrier, polymerization medium, particulant removal fluid, carrier fluid, buffing abrasive agent, displacement drying agent and power cycle working fluid. More particularly, HFC-236fa is a highly effective and environmentally acceptable refrigerant.
Canadian Patent No. 2,073,533 discloses a liquid phase process for the manufacture of HFC-236fa by contacting HCC-230fa with HF in the presence of a liquid phase catalyst (e.g., tin and antimony compounds). All of the 1,1,1,3,3,3-hexachloropropane is converted to 1-chloro-1,1,3,3,3-pentafluoropropane (i.e., HCFC-235fa) and HFC-236fa with a selectivity of greater than 45 mole with respect to HFC-236fa. The separation of pure HFC-236fa is complicated by the presence of HCFC-235fa. Moreover, vapor processes are often preferred because operational advantages (e.g., HF corrosivity problems are typically exacerbated in the liquid phase).
HFC-236fa has been prepared by vapor phase chlorine substitution processes in which the yields have typically been less than about 70%. For example, U.S. Pat. No. 5,171,901 discloses a process for the preparation of HFC-236fa by contacting a mixture of hexachloropropene and HF with a catalyst consisting of a mixture of CrCl.sub.3 and MgF.sub.2 at temperatures ranging from 350.degree. C. to 500.degree. C. The reaction temperatures and yields of HFC-236fa were as follows: 350.degree. C., none detected; 400.degree. C., 10%; 450.degree. C., 55%; and 500.degree. C., 64%. Other products formed in varying amounts were CF.sub.3 CHClCF.sub.3, CF.sub.3 CCl.sub.2 CF.sub.3, CF.sub.3 CCl.dbd.CF.sub.2, CF.sub.3 CCl.dbd.CClF, and CF.sub.3 CCl.dbd.CCl.sub.2.
U.S. Pat. No. 3,859,424 discloses (Example 10) a process for the reaction of 1,1,1,3-tetrachloropropane and HF over a fluorinated chromium oxide catalyst at 200.degree. C. The major product (58%) obtained was 1,1,1-trifluoropropene; the other product (28.5%) was 1,1,1-trifluoro-3-chloropropane.
There is an interest in developing more efficient vapor phase processes for the manufacture of HFC-236fa.